19721642 has 16 divisors (see below), whose sum is σ = 30660864. Its totient is φ = 9513900.

The previous prime is 19721633. The next prime is 19721659. The reversal of 19721642 is 24612791.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 19721599 and 19721608.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59417 + ... + 59747.

It is an arithmetic number, because the mean of its divisors is an integer number (1916304).

Almost surely, 2^19721642 is an apocalyptic number.

19721642 is a deficient number, since it is larger than the sum of its proper divisors (10939222).

19721642 is an frugal number, since it uses more digits than its factorization.

19721642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 426 (or 364 counting only the distinct ones).

The product of its digits is 6048, while the sum is 32.

The square root of 19721642 is about 4440.9055382883. The cubic root of 19721642 is about 270.1765740284.

The spelling of 19721642 in words is "nineteen million, seven hundred twenty-one thousand, six hundred forty-two".